A CT scan anatomical study correlating between the retroversion of the humeral head and the orientation of the inter-tubercular sulcus

The shoulder socket is called the glenoid fossa. This socket is shallow and is part of the scapula (shoulder blade). The surface of the humeral head and the inside of the fossa are covered with articular cartilage. The glenohumeral joint consists of an articulation between the scapula and humerus. Retroversion angle of humeral head (or retrotorsion angle, RA) is an important parameter in total shoulder arthroplasty and is one of these important reference factors which can influence the outcomes of total shoulder arthroplasty. This study was undertaken to evaluate the correlation between retroversion angle of humeral head and position of intertubercular sulcus. The present study is a prospective one which was conducted in the Department of Radiodiagnosis and Imaging at Government Medical College and Hospital, Srinagar. The 60 dry adult humeri were analyzed by multiplanar computed tomography (CT). CT data were transferred to a workstation (Silicon Grafics; Sunnyvale, CA) for multiplanar CT-reformation. The mean retroversion angle of the humeral head in relation of the transe-picondylar axis was 12.3 degree. The mean ITS orientation was 40.7 degree. The Pearson correlation coefficient between the retroversion of the humeral head and the ITS orientation was -0.37. There was an inverse correlation between the retroversion of the humeral head and the ITS orientation. This variation is due to several factors, including the definition of humeral head retroversion, different methods of measurement, ranges of normal values, and accuracy of anatomic landmarks to guide determination of anatomic retroversion. Humeral head retroversion is generally defined with respect to the plane of the humeral head articular surface proximally; distally, however, the reference axis has been debated, including the transepicondylar axis, trochlear tangent axis and forearm axis. The study concludes that there is a reverse correlation between the retroversion of the humeral head and the orientation of the intertubercular sulcus.